The invention is based on a locking device and an associated holding bolt and method therefor as generally defined hereinafter.
In fuel injection pumps of the series type, it is necessary to adjust the supply onset position or a rotary position corresponding to supply onset, for instance of the first cam (counting beginning at the drive mechanism) of the camshaft which here represents the drive shaft and then to lock the camshaft in place, in order to be able to mount the injection pump to the appropriately prepared internal combustion engine. In fuel injection pumps of the distributor type, the drive shaft is locked in the rotary position in which a particular outlet begins to supply fuel, or else it is locked in a position which is offset from this rotary position by a constant amount.
In order to mark this supply onset position fixed on the test bench, it has previously been conventional to provide a slash mark on some elements firmly connected with the drive shaft and to provide a second slash mark, agreeing with the first, on the end face of the pump or on the movable part, if the fixed mark is located on the pump housing. This known manner of adjustment has, among others, the grave disadvantage that the slash marking is difficult or impossible to see from outside if the pump is mounted with an end flange to the gear box of the internal combustion engine. In that case, it is frequency necessary to ascertain the supply onset anew once the pump has been mounted on the engine. This can be accomplished by the so-called "overflow method": with the pressure valve removed, the pump suction chamber is placed under fuel pressure, and with the drive shaft coupled to the pump and stationary the pump is pivoted slowly until such time as the pump piston, upon its upward stroke, closes the intake bore and the fuel stops flowing out. In this position, the injection pump is firmly screwed to the engine, which has already been adjusted to supply onset. This type of adjustment method is very time consuming and can be performed only by experienced personnel. However, even if the slash mark is accessible, the adjustment when the pump is mounted on the engine is very much dependent upon the skill of the mechanic.
It is true that a device of the general type is-also known (German Offenlegungsschrift No. 29 49 100), in which a spring-loaded holding bolt of a locking device which is positionally fixed with respect to the pump housing is pressed by means of a transverse groove on the end face onto a protrusion at the circumference of some element connected with the camshaft of the injection pump, in order to lock the camshaft in the supply onset position during mounting on the engine. The apparatus disclosed there is very expensive and labor-intensive, and the structural unit receiving the holding bolt in a guide bushing must absolutely be removed following the mounting of the injection pump on the engine, and the hollow screw which has been used must be replaced by a closure screw. These devices are then returned by the engine builder to the manufacturer of the injection pump and are used again. This procedure can bring about additional costs and also has the disadvantage that if the injection pump is repaired and then remounted on the engine, the rotary position of the camshaft corresponding to supply onset must be found once again or reascertained by means of a new device which may possibly have different dimensional tolerances. It is the object of the invention to develop a highly simplified locking device which satisfies the demands placed upon it, is inexpensive to manufacture and can remain in place on the injection pump such that it will not be lost and yet will have no disadvantageous effect on engine operation even after the injection pump has been mounted on the engine.